This invention relates to devices for driving fasteners and more particularly to devices of the type including means for resiliently biasing the magazine assembly towards the nosepiece into an operative position so that resilient movement of the magazine assembly away from the nosepiece will take place during an unwanted fastener deformation so as to allow the deformed fastener to self clear after which the magazine is returned to an operative position.
A common problem with all fastener driving devices is inevitable fastener jams which occur when a fastener is being driven from the device. These jams are the result of a fastener becoming deformed and getting stuck in the drive track. The possible causes of such jamming are well-known, numerous and unpreventable. For example, a knot or hard spot in the workpiece or a defective fastener might be the cause. The problem is particularly acute when long thin fasteners are used which are prone to bending when subjected to the force necessary to drive them into the workpiece. The use of power-driven tools further magnifies the problem because of the large forces generated. Additionally, the drive track components are subjected to undesirable deforming stresses resulting from such jams.
In the conventional tool, it is typically necessary to disassemble the tool in order to allow access to the drive track so that the deformed fastener can be removed. This is both inconvenient and time consuming and results in significant downtime for the tool.
More recently, various arrangements have been devised to facilitate such access. Typical of a first type of arrangement has been a nosepiece which pivots forwardly from the drive track. This pivoting action permits the drive track to be exposed and the deformed fastener to be removed. However, these pivoting nosepieces have proven difficult to open when jamming occurs and equally difficult to close due to the large forces required. Extraneous tools have been required to both open and close the nosepiece. Moreover, the nosepiece is larger when the pivoting mechanism is contained therein which can prevent the device from being moved closer to a workpiece if there is an obstruction in front of the device.
A second type of arrangement is exemplified by U.S. Pat. No. 3,840,165 to Howard. In this arrangement, the magazine opens automatically in response to the deformation of a fastener. This automatic release has the advantage of providing fast and convenient access to the drive track to remove fastener jams. The major difficulty encountered with such a device is that they are prone to frequent and undesired releases of the magazine in response to a fastener deformation. These openings reduce the operator's confidence in the tool and can result in the magazine assembly striking and damaging the workpiece.